MEMPHIS (UPI) — A U.S. study has revealed the basis of childhood leukemia resistance to the anti-cancer drug methotrexate.

Scientists at the St. Jude Children’s Research Hospital say their findings provide new insights into the genomic basis of methotrexate resistance and differences in methotrexate response.

The researchers said their study — the first analysis of the genetic determinants of resistance to methotrexate in childhood acute lymphoblastic leukemia, or ALL — could offer a pathway to predicting such resistance and treatments to overcome it.

Besides its use in ALL, methotrexate is widely used to treat other cancers and some autoimmune diseases. However, until the new study there was no valid test for analyzing the genetic basis of resistance. Although 80 percent of children with the disease can be cured, determining the basis of drug resistance in the other 20 percent would help increase the cure rate.

The researchers, led by Dr. William Evans, report their findings in the journal PLoS Medicine.